Organic aluminum complexes



United States Patent 3,448,134 ORGANIC ALUMINUM COMPLEXES Leslie D.McGraw, Weirton. W. Va., assignor, by mesne assignments, to NationalSteel Corporation, Pittsburgh, Pa., a corporation of DelawareApplication June 1, 1966, Ser. No. 560,947, which is a division ofapplication Ser. No. 156,996, Dec. 4, 1961, now Patent No. 3,268,421,dated Aug. 23, 1966. Divided and this application July 3, 1967, Ser. No.650,620 The portion of the term of the patent subsequent to Aug. 23,1983, has been disclairned Int. Cl. C07f /06 U.S. Cl. 260-448 3 ClaimsABSTRACT OF THE DISCLOSURE The complexes ethoxyethyl-trimethyl ammoniumchloride-aluminum halide and ethoxyethyltrimethyl ammoniumchloride-aluminum halohydride are disclosed. The complexes are useful inthe electrodeposition of aluminum from fused baths.

This application is a division of application Ser. No. 560,947, filedJune 1, 1966, by Leslie D. McGraw for Electrodeposition of Metals, nowabandoned. Application Ser. No. 560,947 is a division of applicationSer. No. 156,966, filed Dec. 4, 1961, by Leslie D. McGraW forElectrodeposition of Metals, now United States Patent No. 3,268,421.

This invention broadly relates to the electrodeposition of metals and,in some of its more specific variants, to novel compositions useful asbaths for the electrodeposition of metals and to a process forelectrodepositing metals therefrom. The invention further relates to aprocess for preparing the baths of the invention, additives therefor,and a new chemical compound.

The invention may be illustrated and described hereinafter with specificreference to the electrodeposition of aluminum on a conductive substrateemploying the novel baths of the invention. However, it is understoodthat the invention is not limited thereto and that aluminum alloys, orstill other metals or metal alloys may be electrodeposited from thenovel plating baths of the invention.

A number of processes have been proposed heretofore for thee'lectrodeposition of aluminum. For instance, aluminum may beelectrodeposited from fused inorganic salt baths containing at least 75%by Weight aluminum chloride and the remainder alkali metal chloride, orfrom prior art organic baths comprising a solution of an aluminum saltin a highly inflammable organic solvent such as ethyl ether. Whilesatisfactory aluminum electrodeposits may be obtained from the foregoingbaths, they each have objectionable features. For instance, theinorganic bath fumes excessively at the relatively high operatingtemperature and some means must be provided for controlling the fuming.The organic baths of the prior art do not present a fuming problem butthe organic solvent is inflammable and presents a serious fire hazard atthe operating temperature. As a result, there has long been a need for asatisfactory bath for the electrodeposition of aluminum which does notpresent the fuming problem of the inorganic baths and which isnoninfiammable at the operating temperature.

It is an object of the present invention to provide a novel compositionof matter which is especially useful as a bath for the electrodepositionof metals or metal alloys.

It is a further object to provide a novel plating bath forelectroplating aluminum on a conductive substrate.

It is still a further object to provide additives for the Patented June3, 1969 baths of the invention whereby the initial resistivity may bereduced.

It is still a further object to provide the new chemical compoundethoxyethyltrimethyl ammonium chloride.

It is still a further object to provide a novel process for theelectrodeposition of metals and metal alloys from the baths of theinvention.

It is still a further object to provide a novel process forelectroplating aluminum on a conductive substrate from the novel platingbaths of the invention.

It is still a further object to provide a novel process for preparingthe plating baths of the invention.

Still other objects and advantages of the invention will be apparent tothose skilled in the art upon reference to the following detaileddescription and the specific examples.

In accordance with one variant of the present invention, novelcompositions of matter are provided which consist essentially of anorganic complex of an aluminum halohydride, with or without an organiccomplex of an aluminum halide. The resultant compositions are useful forthe deposition of metal on a substrate, and they are especially usefulas a bath in the novel process of the invention for theelectrodeposition of a metallic material on a conductive substrate.

In accordance with a more specific variant of the invention, novel bathsare provided for the electrodeposition of a metallic material on aconductive substrate which consist essentially of an etherate of analuminum halohydride, with or without an etherate of aluminum halide.The resultant baths are noninflammable at the operating temperature,i.e., the temperature at Which the metallic material may beelectrodeposited on the substrate. Preferably, the metallic materialcomprises aluminum.

The aluminum halohydrides suitable for practicing the present inventionmay include complexes of compounds of the general formula AlH X where Xis halogen, m and n each have a numerical value of at least one, andm-l-n are equal to three. Thus, in the foregoing general formula theatomic ratio of Al to H is between 1:1 and 1:2, the atomic ratio of Alto X is between 1:2 and 1:1, and the atomic ratio of Al to H+-X is 1:3.Specific examples of aluminum halohydrides include AlHX AlH X, andmixtures thereof such as A1 H X which may be written as AlH X for thepurpose of this discussion. Chlorine and bromine are preferred overother halogens in most instances.

Preferably the foregoing aluminum halohydroxides are present in the formof coordinate covalent complexes. The complexes may be prepared byreacting the aluminum halohydroxide with one or a mixture of compoundswhich are known to be complexing agents therefor and especially Lewisbases such as ethers or suitable compounds in general containing afunctional group which is capable of complexing aluminum halohydroxideand/ or aluminum halide, such as organic compounds containing a divalentsulfur atom including the thioethers, organic compounds containing atrivalent nitrogen atom such as the amines, and organic compoundscontaining a trivalent phosphorus atom. An ether or a mixture of ethersis usually preferred as the complexing agent. A Wide variety of ethersmay be employed in forming the resultant etherate such as ethyl ether,propyl ether, 'butyl ether, octyl ether, etc. and ethers in generalwherein the organic groups attached to the oxygen atom contain, forexample, about 1 to 8-20 carbon atoms. The ether may contain an aromaticgroup such as methylphenyl ether, ethylphenyl ether, diphenyl ether,etc., or a cyclohydrocarbon radical and especially those containingcarbon atoms within the foregoing ranges. Ethers containing a pluralityof ether linkages and organic radicals as above discussed or theirequivalents also may be used, such as diethylene glycol diethyl ether,or cyclic ethers such as tetrahydrofurane. Diethyl ether or a mixture ofothers comprising diethyl ether is usually preferred.

If desired, an organic complex of aluminum halide may be present in thecomposition and this is usually preferred. The complexing agents for thealuminum halide may be the same as discussed above for the aluminumhalohydrides and, similarly, the preferred complexing agent is an etheror a mixture of ethers of the types discussed above. Preferably, thealuminum halide is aluminum chloride or aluminum bromide.

The complexes of alu-minum halides or aluminum halohydrides may beprepared by a number of methods. For instance, previously preparedaluminum halohydride and/ or aluminum halide may be dissolved, in asolvent, the complexing agent added to the solution, and the mixturereacted to produce the desired complex, or a mixture of the twocomplexes when both aluminum halohydroxide and aluminum halide arepresent in the solution. The solvent may be removed subsequent to thecomplexing step by evaporation and/ or aeration with a dry inert gas toan extent to render the resultant composition noninflammable at theoperating temperature of a bath prepared therefrom. Usually, it is moreconvenient to prepare an aluminum halohydride-containing complex bydissolving aluminum halide in a solvent, adding the complexing agent andan active hydrogen-containing compound to the solution in an amount toprovide the desired amount of active hydrogen in the resultantcomposition, and reacting the mixture to produce a complex of aluminumhalohydride. In instances Where the aluminum halide is present inexcess, a mixture of the complexes of aluminum halohydride and aluminumhalide is produced. The solvent and complexing agent may be the samesubstance, such as when an ether is used as the solvent and complexingagent. The solvent may be removed subsequent to the reaction as notedabove and the reaction product used in preparing the baths of theinvention.

When an etherate of an aluminum halohydride is prepared, preferablyaluminum halide is dissolved in an excess of diethyl ether and then oneor a mixture of metal hydrides such as aluminum hydride, alkali metalhydrides such as sodium, potassium or lithium aluminum hydride, oralkaline earth metal hydirdes such a calcium hydride, is added to thesolution in the calculated quantity to provide the desired amount ofactive hydrogen in the resultant composition. The metal hydride may beadded in the calculated amount to react with the aluminum halide andproduce a desired aluminum halohydride etherate, or in a smaller amountso as to have the aluminum halohydride etherate present in solutiontogether with aluminum chloride etherate. When metal hydride is reactedwith aluminum halide, preferably the mole ratio of aluminum hydride (AlHto aluminum halide (A1X3) in the resultant aluminumhalohydride-containing composition is between 1:05 and 1:22, and forbetter results between 1:2 and 1:11. In the present specificiation andincluding the claims, for convenience the mole ratio of aluminum hydride(AlH to aluminum halide (AlXg) in the aluminum halohydride-containingbath compositions of the invention is calculated by considering thealuminum halohydride content to be a mixture of AlH and AlX and freealuminum halide, if any, is added thereto. For example, a bathcomposition containing only three moles of an etherate of AlH wouldcontain one mole of All-I for each of two moles of AlCl and the AlH toA101 ratio would be 1:2. If the bath also contained one mole of anetherate of free aluminum chloride for each three moles of AlHCl2, thenthe AlH to A101 ratio would be 1:3 due to the presence of the excessaluminum chloride.

After reaction of the metal hydride with the ether solution of aluminumhalide, the excess ether over that ,4 required to form the etherate maybe evaporated by heating and/ or aeration with a dry inert gas. Theether solution often may be merely heated to its boiling point and thefree or solvent ether boiled off. When this is done,

the boiling point of the resultant composition rises slowly withevaporation of ether until the monoetherate of the aluminum halohydrideand aluminum halide is formed. When diethyl ether is used as thesolvent, the flash point of the resultant composition will rise to about200- 215 F. and there is no further appreciable rise. The resultantcomposition is noninflammable and may be decanted and used as a platingbath. When the ether is diethyl ether, preferably the solvent ether isremoved by boiling the solution until the boiling point rises to about-10 F. Then, a dry inert gas such as nitrogen, helium, argon, etc., ispassed through the composition at a lower temperature such as 90 F. forthe purpose of removing an additional amount of solvent ether andraising the flash point up to about 200-215 F. This latter procedure hasthe advantage of reducing thermal decomposition and thermaldecomposition may be further reduced by using only aeration with dry,inert gas at temperatures of 70-90 F. for removing the solvent.Anhydrous conditions should be maintained throughout the reaction andduring the removal of excess ether for the purpose of preventingdecomposition of the aluminum halohydride.

The plating baths of the present invention preferably are treated toremove organic solvent until the vapor phase in equilibrium with thebath at the operating temperature is nonexplosive and noninflammable inair. When diethyl ether is the solvent, the ether content of the vaporphase should not be greater than about 1% by volume in most instances.The ether content that remains is largely combined chemically with thealuminum halohydride and aluminum chloride in the form of etherates. Theetherates are stable at the operating temperature of the bath, and thusother is not available in the free or uncombined form for forming acombustible or explosive mixture. The resultant noninflammable aluminumhalohydride-containing compositions may be used in preparing baths forthe elec tro-deposition of a metal such as aluminum or aluminum alloys.

The thermal stability of the bath is often improved when excess or freealuminum halide complex is present. Usually, the mole ratio of AlH toA101 should not be higher than about 1:3, and preferably not higher thanabout 1:6. The bath should be at least 1 molar in active hydrogen, i.e.,at least one molar in AlHCl or the equivalent in active hydrogencontent. The plating baths of the invention generally may be used attemperatures above the melting point and below the decomposition point.The optimum operating temperature for specific baths may vary somewhat,but usually temperatures about 520 F. above the melting point and belowabout F. are satisfactory when the complexing agent is diethyl ether.The current density may vary over wide ranges. For example, the lowerlimit is largely practical in nature and may be 0.1-1 ampere/sq. ft.,While the upper limit may be 50-150 amperes/sq. ft. or higher.

Excellent plate may be produced from the above described baths but theresistivity is often of the order of about 1200-1300 ohm-centimeters andthus the power consumption is high. It has been further discovered thatthe resistivity may be reduced by dissolving in the baths at least onesoluble ionizable compound such as quaternary ammonium compounds, aminesalts, and nonoxygeucontaining mineral acids and salts thereof in anamount to lower the initial resistivity. By this method, often theinitial resistivity of 1200-1300 ohm-centimeters may be reduced to about600-700 ohm-centimeters or lower. It is usually not possible to furtherreduce the resistivity below this level due to the relatively lowsolubility of such substances in the baths, which may be about 0.5% to5-10%. In most instances, the ionizable compound is dissolved in thebath to the extent of its solubility, but smaller amounts may reduce theresistivity somewhat.

A wide variety of compounds of the foregoing types may be dissolved inthe plating baths of the present invention. Examples of quaternaryammonium compounds include quaternary amine salts and pyridiniumcompounds wherein the organic radicals attached to the nitrogen atom maycontain 1-8 to 20 carbon atoms. Specific examples include tetramethyl,tetraethyl, tetrapropyl, tetrabutyl, tetraamyl, tetrahexyl, tetraoctyland higher ammonium halides or other suitable salts ofnonoxygen-containing mineral acids. The organic radicals attached to thenitrogen atom may or may not be the same. For example, dodecyl trimethylammonium chloride and equivalent mixed quaternary ammonium salts may beused. Pyridinium compounds include methyl, propyl, amyl, octyl andhigher alkyl pyridinium nonoxygen-containing mineral acid salts whereinthe alkyl radical contains, for example, 1-8 to 20 carbon atoms. Thenonoxygen-containing mineral acid salts of the pyridinium compoundsinclude halides such as chlorides, bromides, etc. Inorganic saltsinclude alkali metal nonoxygen-containing mineral acid salts, alkalineearth metal nonoxygen-containing mineral acid salts, andnonoxygen-containing mineral acid salts in general which are soluble inan amount to reduce the resistivity of the bath. Specific examplesinclude the halides of the foregoing groups of metals and especially thechlorides and bromides. Lithium chloride is usually preferred.

The amine salts may be derived from amines containing 1 to 3 organicradicals attached to the nitrogen atom having 1-8 to 20 carbon atoms.Preferably, the organic radicals are alkyl and the salts are formed froma nonoxygen-containing mineral acid such as hydrochloric, hydrobromic,etc. Still other ionizable compounds include nonoxygen-containingmineral acids such as the hydrogen halides and alkali or alkaline earthmetal salts thereof, and especially organic derivatives wherein at leastone ionizable hydrogen atom of the mineral acid has been replaced by anorganic radical containing, for example, 1-8 to 20 carbon atoms. Theresultant organic compound containing a mineral acid group or the alkalior alkaline earth metal salt thereof may be dissolved in the bath tosome extent, and the resistivity is reduced due to the ion ization ofthe mineral acid substituent.

Ionizable compounds of the above types may reduce the initialresistivity of the basic bath to about 600-700 ohm-centimeters. Theresultant bath may be used, as may the basic bath, for theelectrodeposition of very satisfactory electrodeposits of a coatingmetal such as aluminum, aluminum alloys, or other metals mentionedherein. However, the power consumption is higher than ideal incommercial installations and it is usually desirable that theresistivity be reduced still lower.

In accordance with another variant of the invention, it has beendiscovered that the resistivity of the basic bath may be reduced a stillgreater extent by means of a difunctional compound having a complexingfunction for the aluminum halohydride and/ or aluminum halideconstituents of the bath and, in addition thereto, an ionizablesubstituent. Since the difunctional compound is both a complexing agentand an ionizable compound and complexes the aluminum halohydride and/oraluminum halide, it is soluble in the bath in large amounts and theionizable substituent is likewise solubilized in large amounts. Due tothe increase in the concentration of the ionizable substituent and theavailability of additional ions for carrying the current, the initialresistivity of the basic bath may be reduced markedly to about 70ohm-centimeters or lower. This may be accomplished without a decrease inthe flash point and the bath remains noninfiammable at the operatingtemperature.

The difunctional compounds may contain the same types of complexinggroups that are present in the simple complexing agents previouslydescribed and, similarly, the

same types of ionizable groups that are present in the ionizablecompounds previously described. Thus, the difunctional compound may beconsidered to be a complexing agent of the types previously describedwhich is also an ionizable compound selected from the group consistingof quaternary ammonium compounds, amine salts, and organic compoundscontaining a nonoxygencontaining mineral acid group and salts thereof asdefied herein.

Usually it is preferred that about 33-66 mole percent of the totalamount of complexing agent contain an ionizable substituent. However, insome instances amounts as low as 15-25 mole percent and up to 75-85percent may be used. Even 1 mole percent improves the conductivity.

Ethers are the preferred complexing agents and quaternary amine saltsare the preferred ionizable compounds. In instances where both the etherlinkage and quaternary amine group are present in the same molecule, thecompounds may be of the following classes:

where R and R" are monovalent organic radicals containing up to about 20carbon atoms and preferably l-8 carbon atoms, R is a divalent organicradical containing up to about 20 carbon atoms and preferably 1-8 carbonatoms, and Y is a nonoxygen-containing mineral acid residue such ashalogen, etc. In most instances, alkyl or alkylene radicals containing1-8 carbon atoms are pre ferred.

Of the above types of compounds, ethoxyethyltrimethyl ammonium chlorideis preferred. Other specific ethers containing quaternary ammoniumgroups which may be used are methoxymethyltrimethyl ammonium halidessuch as the chloride, bis(Z-dimethylaminoethyl)ether dimethhalides suchas the chloride, N-ethyl-N-methyl morpholinium halides such as theiodide or chloride and 2-ethoxyethyltriethyl ammonium halides such asthe iodide or chloride.

In instances where the plating bath contains aluminum chloride, aluminumdichlorohydride, ethyl ether, and

ethoxyethyltrimethyl ammonium chloride, the following compositions areespecially useful:

The preferred bath above defined has a melting point of approximately 90F. The operating temperature range for the electrodeposition of aluminumor aluminum alloy therefrom is above the melting point and preferablybelow about 160170 F. Best results are usually obtained at an operatingtemperature of about -135 F.

The lower limit on the current density to be employed is practical innature, and current densities as low as 0.1 to 1 ampere/ sq. ft. may beused. Current densities as high as -300 amperes/sq. ft. may be used withthe preferred baths, and often as high as 1000 amperes/sq. ft. ininstances where the preferred additives for reducing resistivity areused. Generally, when additives for reducing resistivity are notpresent, current densities up to 50-150 amperes/ sq. ft. will givebetter results. Special plating conditions may be used if desired suchas pulse current, polarity reverse current, etc., or the plating may beconducted with vigorous agitation, rotating or rapidly moving cathodes,etc.

The coating metal may be supplied to the plating bath by any suitableconvenient means such as by addition of a soluble salt of the coatingmetal, by soluble anodes, or by auxiliary anodes. In the specificationand claims, it is understood that an electroplating bath of theinvention contains the metal or metals to be electrodeposited on thesubstrate in a form that may be electroplated therefrom. When analuminum-containing coating is electrodeposited, preferably aluminumanodes or aluminum alloy anodes are immersed in the bath in the usualmanner. Other metals that may be electrodeposited include titanium,zirconium, vanadium, columbium, beryllium, molybdenum, tungsten,chromium, tantalum, magnesium, manganese, nickel, cobalt, iron, copper,and alloys thereof with or without aluminum. Preferably, in instanceswhere aluminum is being deposited and iron is present in the bath, theconcentration of iron is maintained below 0.2% by weight, and preferablybetween 0.01 and 0.02%.

The thickness of the aluminum plate may vary over wide ranges. Usually,for strip plating thin deposits are preferred such as 15x10" to 90 10inch. However, much heavier deposits are possible such as up to severalthousandths of an inch, e.g., X10 to 10 inch, or even up to /s to /2inch. It is also possible to use the plating bath of the presentinvention for electroforming. When so used, preferably additives arepresent which tend to reduce treeing. ,B,B'-Dichloroethyl ether may beused as an addition agent to improve the smoothness and hardness of theplating, regardless of whether electroplating items such as steel stripor in electroforming. This ether may be added in an amount sufficient toconstitute 4-8% by volume of the bath, but smaller or larger amounts maybe added in some instances.

The coating metals described herein may be electrodeposited on anysuitable conductive substrate. Prefer ably, the substrate is ferrousmetal in the form of strip, wire, or other metal articles. Still othermetallic substrates may be used if desired, as may normallynonconductive substrates which have been treated with a conductor torender them conductive for purposes of the present invention. Suchmaterials are well known and the selection of a specific conductivesubstrate for practicing the present invention is within the skill ofthe art.

It is preferred that metallic substrates such as ferrous metal beactivated or etched prior to the electrodeposition of aluminum. This maybe done by an suitable method know to the art, such as by treatment withhydrogen chloride gas in a carrier gas. In one preferred method, themetal is dipped in a long chain fatty acid such as ole-ic, rinsed in anether solution of aluminum halohydride, and then plated. In anotherpreferred method, the metal is cleaned mechanically in an anhydrousatmosphere to provide a fresh, clean surface. For best results theforegoing treatments should be effected under anhydrous conditions.

Preferably the free solvent content of the bath is maintained at a levelsufficiently low to provide an ignition point as determined by ASTMD286-58T that is above the operating temperature of the bath and usuallyabove 500 F. Also, the bath should be prepared under -anhydrousconditions and maintained substantially anhydrous throughout its life.For instance, the bath should not contain the decomposition products ofover about 1% by weight of water when such water has been deactivated bytreatment of the bath with a metal hydride in an amount to provide atleast about two gram atoms of active hydrogen per mole of water.Additionally, the bath should not contain over about 0.020.03% of waterwhich has not been deactivated by addition of a metal hydride as atwater concentrations greater than this the bath is detrimentallyaffected. Within the above limits, a bath containing water may berestored to its former condition and excellent plate again obtained byaddition of the metal hydride in the prescribed amounts.

As disclosed in my copending application Ser. No. 159,477, filed Dec.14, 1961, for Process for the Deposition of Metals and the ResultantProducts, the halohydride-containing compositions of the invention maybe used in the electroless deposition of metallic aluminumcontainingmaterial on a wide variety of bases or substrates including metals suchas ferrous metal, brass, copper, etc., and nonmetallic substrates suchas wood, composition board, plastics, etc. This may be convenientlyaccomplished by decomposing an aluminum halide-containing composition ofthe invention to produce metallic aluminum in intimate contact with thesubstrate on which the aluminum is to be deposited. The decompositionmay be etfected by heating a body of the composition from a lowertemperature up to or above the decomposition temperature while inintimate contact with the substrate, or the substrate may be heatedabove the decomposition temperature and contacted with the composition.

Where the melting point of a specific bath composition is undesirablyhigh, a noninfiammable liquid or low melting point diluent which is notdetrimental to the electrodeposition of a metal therefrom may be addedto reduce the melting point. Preferably, the diluent is inert withrespect to the bath at the temperatures encountered.

The foregoing detailed description and the following specific examplesare for purposes of illustration only and are not limiting to the spir-tor scope of the appended claims.

EXAMPLE I The monoetherate of All- C1 was prepared by treating aluminumchloride in ether solution with lithium aluminum hydride in thecalculated amount to form AlHCl Excess or solvent ether was evaporatedfrom the resultant product, and the ether content further reduced to themonoetherate of AlHCl by aeration with dry gaseous nitrogen.

The resultant monoe-therate of All- C1 was heated to the moltencondition, alumnium anodes immersed therein, and the resultant bath usedfor plating steel panels at 30 amperes/sq. ft. at temperatures of 82 F.and 115 F. A thickness of about 0.03 mil of aluminum was deposited onthe steel panels in the form of an adherent white mat plate which couldbe roll brightened.

The resistivity of the bath was determined and found to be 309ohm-centimeters at F. The bath was tested and found to be noninfiammableat the plating temperatures.

EXAMPLE II A plating bath was prepared by dissolving aluminum chloridein diethyl ether, and .then treating the solution with lithium aluminumhydride in the calculated amount to produce 2 moles of AlHCl for each3.8 moles of aluminum chloride remaining in the ether solution. Excessether was evaporated from the resultant product to produce themonoetherates of the AlHCl and AlCl The above prepared compositioncontained 2 moles of aluminum dichlorohydrate etherate for each 3.8moles of aluminum chloride etherate. The composition was used as aplating bath for electrodeposi-ting aluminum on ferrous metal panels at30 amperes/ sq. ft. and at a temperature of F. Aluminum anodes wereimmersed in the plating bath during the electrodeposition.

The aluminum plated out on the ferrous metal panels in the form of awhite mat coating and was pleasing in appearance, adherent, and could beobtained in any desired thickness. The white mat plate could be rollbrightened, or other forms of brightening could be used.

If desired, the corresponding aluminum bromide salt may be prepared byusing aluminum bromide as the starting material. The resultant bathcould be used for the electrodeposition of aluminum.

of 2-chloroethyl ethyl ether and grams (0.55 mole) of 25% triethyl aminein methanol in a steel bomb at 125 C. for 15 hours. Thereafter, themixture was evaporated to a syrup on a rotating evaporator at 70 C.,dissolved in ethyl alcohol (100 ml.) and evaporated to dryness, Theproduct was dispersed in acetone, filtered with suction while preventingcontact with moisture, and then dried in vacuum at 80 C. The resultantproduct was 70.1 grams of a white solid (83.5% of the theoretical yield)which was identified as being Z-ethoxyethyltrimethyl ammonium chloride.

The above procedure was modified somewhat by dis solving 123 grams (1.13moles) of 2-chloroethyl ethyl ether and 307 grams (1.3 moles) of 25%trimethyl amine in methanol, and heating in a glass bottle at 70 C. for15 hours. Thereafter, the product was evaporated to dryness using arotating evaporator at 70 C., the product dispersed in ethyl alcohol(200 ml.) and evaporated to dryness, repeated, slurried with acetone,filtered with suction, washed with acetone and pentane, and then driedin vacuum at 80 C. overnight.

The resultant product was 152.1 grams of off-white crystalline solid(30.2% of the theoretical yield), and this likewise was identified asbeing 2-ethoxyethyltrimethyl ammonium chloride.

EXAMPLE IV Lithium hydride was added to a diethyl ether solution ofaluminum chloride in the calculated amount to produce 2 moles ofaluminum dichlorohydride for each 3.8 moles of aluminum chlorideremaining in the solution. The resultant ether solution contained excesssolvent or free ether, which was evaporated by heating to the boilingpoint of the bath.

With continued evaporation, the boiling point of the bath gradually roseuntil a temperature of 160 F. was reached. At this point, the bath wascooled and dry nitrogen was bubbled through the bath at about roomtemperature to thereby strip the remaining ether out of the bath andproduce a mixture of the monoetherate of aluminum dichlorohydride andthe monoetherate of aluminum chlo' ride. At this point, the flash pointof the bath was about 200-215 F and no further rise of the flash pointwas noted with continued stripping with the nitrogen. The resultant bathhad a melting point of about 90 F., and was used as a plating bath forthe electrodeposition of aluminum.

Aluminum anodes were immersed in the bath and aluminum' electrodepositedon steel panels at temperatures from slightly above the melting point upto a temperature just below the decomposition point (about 160-175 F.).The preferred temperature range was found to be 115- 135 F. Currentdensities between 0.1 ampere/sq. ft. and 150 amperes/sq. ft. andpreferably l-l00 amperes/sq. ft. could be used to produce white mataluminum plate of good quality.

The resistivity of the above bath was about 1200-1300 ohm-centimetersand it was noninflammable at the operat ing temperatures.

EXAMPLE V A plating bath is prepared in accordance with the procedure ofExample IV, the bath divided into a number of portions and then each ofthe portions is saturated with one of a number of ionizable compounds.The bath and a resistivity of about 1200-1300 ohm-centimeters. Ioniz-EXAMPLE VI A plating bath was prepared from the following:

Moles AlCl 3.8 AlHCl 2.0 Ethyl other 3.8 2-ethoxyethyltrimethyl ammoniumchloride 2 The above composition was heated to the melting point. Theresultant bath was essentially a monoetherate of aluminum chloride plusa monoetherate of aluminum chlorohydride, of which 2 moles of the etheris 2-eth0Xyethyltrimethyl ammonium chloride.

The above bath was noninflammable and had a resistivity of approximatelyohm-centimeters. When used for the electrodeposition of aluminum onsteel panels, the bath produced excellent mat aluminum plate at currentdensities up to 300 amperes/ sq. ft. The preferred temperature ofelectrodeposition was -135 F. Aluminum deposits of any desired thicknesscould be produced, and the bath could be used for electroforming.

I claim:

1. A substance selected from the group consisting of complexes havingthe formulae ethoxyethyltrimetyl ammonium chloride-aluminum halide andethoxyethyltrimethyl ammonium chloride-aluminum halohydride.

2. A substance in accordance with claim 1 wherein the complex isethoxyethyltrimethyl ammonium chloride-aluminum: chloride.

3. A substance in accordance with claim 1 wherein the complex isethoxyethyltrimethyl ammonium chloride-aluminum chlorohydride.

References Cited Couch, Dwight E. et al.: A Hydride Bath for theElectrodeposition of Aluminum, Journal of the Electrochemical Society,vol. 99, No.6 pp. 234-244, 1952.

JOHN H. MACK, Primary Examiner.

G. L. KAPLAN, Assistant Examiner.

US. Cl. X.R. 204-39 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3 ,448,l34 June 3 1969 Leslie D. McGraw It iscertified that error appears in the above identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 2 line 49, "halohydrxifis" sfi o uld read halohydrides lines 52and 56, "halohydroxide" each occurrence, should read halohydride Column3, line 4, "tetrahydrofurane" should read tetrahydrofuran line 20,"halohydroxide" should read halohydride line 46, "hydirdes" should readhydrides line 67, AlH should read AlHCl Column 4, line L4, "l50lO F.should read l50-l60- F. Column 9, line 21 "30. 2%" should read 80. 2%line 62, "and" should read had Signed and sealed this 21st day of April1970.

SEAL) Lttest:

'ldward M. Fletcher, Jr. E.

Lttesting Officer Commissioner of Patents

